US7658826B2 - Reference electrode - Google Patents
Reference electrode Download PDFInfo
- Publication number
- US7658826B2 US7658826B2 US11/070,329 US7032905A US7658826B2 US 7658826 B2 US7658826 B2 US 7658826B2 US 7032905 A US7032905 A US 7032905A US 7658826 B2 US7658826 B2 US 7658826B2
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- metal salt
- layer
- water
- reference electrode
- alkali metal
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
- G01N27/28—Electrolytic cell components
- G01N27/30—Electrodes, e.g. test electrodes; Half-cells
- G01N27/301—Reference electrodes
Definitions
- the present invention relates generally to reference electrodes for use in combination with a sensor electrode to qualitatively and/or quantitatively determine the presence of a selected ion in a liquid medium using potentiometric analysis and, more particularly, to a rapidly equilibrated reference electrode which does not require internal water-based electrolytes.
- Reference electrodes are used in potentiometric analysis of qualitative and/or quantitative analyses of ions in solution. There are a variety of such electrodes, utilizing different electrode chemistry, including silver/silver chloride, calomel, and mercury/mercurous sulfate electrodes, as examples. Generally, such reference electrodes use internal aqueous electrolyte solutions and are designed and intended for long-term, repeated use.
- a liquid junction-free reference electrode system is described in “Solvent-Processible Polymer Membrane-Based Liquid Junction-Free Reference Electrode,” by Hyuk Jin Lee et al., Anal. Chem. 70, pages 3377-3383 (1998). Therein, the authors describe the use of solvent-processible polymer membranes for forming liquid junction-free reference electrodes in a planar solid-state format.
- a polyurethane matrix reference site was formed on an aluminum oxide onto which silver electrodes were printed by incorporating both cation- and anion-exchange sites (for example, potassium tetrakis(p-chlorophenyl)borate and tridodecylmethylammonium chloride) into a polyurethane matrix, and dispensing (screen-printing) a small volume of this material, typically 5 ⁇ L, onto the silver electrode and the surrounding dielectric layer.
- the sensors were dried in ambient air for 12 h.
- Disposable Reference Electrode by A. Mroz et al., Analyst 123, pages 1373-1376 (1998), the authors describe a disposable reference electrode which includes an Ag/AgCl electrode without a diaphragm, where an internal electrolyte KCl aqueous solution is enclosed in a glass-fiber filter medium in contact with a screen-printed Ag/AgCl strip conductor. The lower part of the electrode is cut open before the electrode is used.
- Another object of the invention is to provide inexpensive, disposable and stable reference electrodes which do not require calibration.
- the reference electrode hereof includes: a water-impermeable, non-conductive substrate having a surface; an electrically conductive metal/metal salt layer disposed on the surface of the substrate; a water-soluble alkali metal salt layer disposed on the surface of the substrate and in contact with at least a portion of the metal/metal salt layer; and a water-impermeable barrier layer overlaying a portion of the alkali metal salt layer, and a portion of the metal/metal salt layer.
- the method for generating a reference electrode hereof includes the steps of: forming an electrically conductive metal/metal salt layer on the surface of a water-impermeable, non-conductive substrate; forming a water-soluble alkali metal salt layer on the surface of the substrate and in contact with at least a portion of the metal/metal salt layer; and overlaying a portion of the alkali metal salt layer, and a portion of the metal/metal salt layer with a water-impermeable barrier layer.
- Benefits and advantages of the present invention include, but are not limited to, a stable, inexpensive, disposable reference electrode which does not require calibration.
- FIG. 1 is an exploded schematic representation of one embodiment of the reference electrode of the present invention.
- FIG. 2 is a schematic representation of a top view of the assembled reference electrode illustrated in FIG. 1 hereof.
- FIG. 3 is schematic representation of a side view of the assembled reference electrode illustrated in FIG. 1 hereof.
- FIG. 4 is a graph of the measured electrical potentials for several reference electrodes prepared in accordance with the teachings of the present invention when compared with a commercially available reference electrode, as a function of time, illustrating the time for the electrode to reach an equilibrium potential.
- FIG. 5 is a graph of the measured electrical potential of a reference electrode prepared in accordance with the teachings of the present invention when compared with a commercially available reference electrode, as a function of time, illustrating the stability of the present reference electrode.
- the present invention includes a stable, inexpensive, disposable reference electrode having no internal aqueous electrolyte solution, and a method for preparing same.
- the reference electrode is thin, compact and easy to use, and may comprise: a water-impermeable, non-conductive substrate having a surface; an electrically conductive metal/metal salt mixture layer disposed on the surface; a water-soluble alkali metal salt layer, wherein the anion of the alkali metal salt is the same as the anion of the metal salt in the metal/metal salt; and a water-impermeable barrier layer overlaying a portion of the alkali metal salt layer and a portion of the metal/metal salt layer, wherein at least a portion of the alkali metal salt layer remains exposed.
- the reference electrode When the reference electrode is placed in an aqueous sample to be tested, water enters the exposed portion of the second layer where it dissolves the alkali metal salt. As the water proceeds toward the metal/metal salt layer, the alkali metal salt becomes more concentrated in the solution. Upon reaching the metal/metal halide layer, the solution is saturated with the alkali metal salt. It is believed by the present inventor that the salt layer takes up or imbibes water from the solution to be investigated by capillary action. The metal salt in the metal/metal salt layer is substantially insoluble.
- the metal/metal salt layer and salt layers may be screen printed or stenciled onto the supporting substrate, but other procedures are anticipated.
- the mask or barrier layer covering the metal/metal salt layer and the salt layer may include pressure-sensitive adhesive tape, although other barrier layers such as thermoplastic polymers, as examples, should provide the required properties. A portion of the metal/metal salt layer is exposed such that an electrical connection may be made thereto for achieving measurements of the electric potential of the reference electrode.
- the reference electrode is intended for use with ion-selective electrodes disposed either on the same substrate therewith or otherwise located in a solution of ions, the concentration of which is intended to be determined by potentiometric measurements.
- a generally planar surface for the substrate has been found to be suitable for the practice of the present invention.
- FIG. 1 an exploded schematic representation of one embodiment of the reference electrode, 10 , of the present invention is shown.
- Electrically conductive layer, 12 which includes a metal/metal salt mixture in a binder, is formed on the generally planar surface of water-impermeable, non-conductive substrate, 14 .
- the metal/metal salt mixture may be silver/silver chloride, silver/silver bromide or silver/silver iodide, as examples.
- the binder may be a plastic material such as polystyrene or polyester, as examples.
- Substrate 14 may be flexible or rigid. A flexible plastic strip may be used. A ceramic strip may also be used.
- Alkali metal salt layer, 16 is also formed on substrate 14 in contact with metal/metal salt layer 12 .
- the anion of the alkali metal salt may be the same as the anion in conductive layer 12 .
- the alkali metal salt may be KCl, KBr or Kl, as examples.
- Water impermeable barrier, 18 overlays alkali metal salt layer 16 and a portion of metal/metal salt layer 12 such that when reference electrode 10 is placed into a water sample, water may enter the second layer through opening, 20 , between barrier 18 and substrate 14 , by means of capillary action.
- the barrier layer may be an adhesive tape or a thermoplastic polymer, as examples.
- Length, 22 , of alkali metal salt layer 16 is chosen such that water being imbibed or taken up by the layer becomes saturated with the alkali metal salt present in the second layer in the vicinity of metal/metal salt layer 12 (4 mm was the length chosen for the present reference electrodes, but the invention should not be limited to this value). Electrodes having overlap, 24 , of metal salt layer 16 with metal/metal salt layer 12 have been prepared and successfully tested (between about 0.02 mm and 1 mm, as an example). It is believed, however, that depending on the thicknesses of layers 12 and 16 , the present reference electrode would function if the ends of the two layers were merely in contact, as opposed to overlapping.
- Alkali metal salt layer 16 may include a material such as diatomaceous earth to provide porosity and to provide some thickness to the layer.
- Layer 16 is prepared to be of a consistency such that it may be printed onto substrate 14 by screen printing, stenciling or other suitable coating processes.
- a water-soluble binder has been found to be necessary in order to establish a robust deposited layer after drying.
- Polyethylene oxide is an example of a suitable binder.
- FIGS. 1-3 hereof illustrate the geometry of the alkali metal salt layer as being generally triangular; however, any geometry may be used as long as the solution is saturated with the alkali metal salt in the region of overlap 24 with metal/metal salt layer 12 when the electrode is in use.
- the reference electrode of the present invention will substantially reach its equilibrium potential. Moreover, the electrode is quite stable in that it will remain at substantially the same potential for an extended period (more than 1 h, as an example).
- EXAMPLE provides more specific details of layer formulations for two ion-selective electrodes.
- Polystyrene (melt index 14 ) is added to approximately 425 g of First Solvent, and the mixture heated to near reflux temperature with vigorous stirring heat the mixture to near reflux temperature for several hours to fully dissolve the polystyrene pellets.
- the mixture is filtered to remove the product, and the filtered product washed with about 2 L of water in small portions to remove the KNO 3 present.
- the resulting washed product is further washed with approximately 500 mL of Methanol to remove the bulk of the water, and the methanol-washed product vacuum dried. Oven drying has been found to create lumps that are difficult to process into the finished printable suspension.
- the yield is between 99 g and 100 g.
- BYK 065 and BYK 202 are commercially available additives for inks and paints, and the like.
- BYK 065 is a solution of polysiloxanes used for preventing foam and bubble formation
- BYK 202 is a solution of an alkylammonium salt of a polycarboxylic acid for control of flocculation, wetting and dispersing of materials such as pigments in inks and paints, and the like.
- materials such as pigments in inks and paints, and the like.
- a solvent mixture having the approximate ratios of 15:45:40 by volume is prepared by mixing 15 mL of Acetophenone, 45 mL of Benzyl alcohol, and 40 mL of p-Cymene, this solvent mixture being hereinafter referred to as the Second Solvent.
- About 25 g of Poly(ethylene oxide) (PEO, Avg. M.W. 300,000) is added to approximately 475 g of Second Solvent with vigorous stirring. After the solid has been added, the mixture is heated without refluxing to dissolve the PEO. The resulting solution is examined for undissolved polymer material.
- PEO Poly(ethylene oxide)
- the Ag/AgCl suspension was printed onto the upper surface of a flexible plastic strip as a substrate, and dried for approximately 8 h under reduced pressure.
- the resulting layer thickness was about 0.01 mm, after the dried, approximately 0.02 mm layer was pressed to reduce layer resistance (by about a factor of 3).
- the alkali metal salt layer (KCl) was coated onto the substrate with a portion thereof overlapping the Ag/AgCl layer, followed by drying. Resulting layer thicknesses were between about 0.05 and 1 mm.
- the mask or barrier layer was then applied to the Ag/AgCl and KCl layers.
- FIG. 4 is a graph of the measured electrical potentials for several reference electrodes prepared as described hereinabove when compared with a commercially available Orion Sleeve Junction Ag/AgCl reference electrode, as a function of time, illustrating the time for the electrode to reach an equilibrium potential. Note that the measured potential differs by less than 0.17 mV among the 10 electrodes after 30 s of immersion. More recent data for reference electrodes fabricated in accordance with the present invention illustrates substantially the same time to reach equilibrium, but a measured electrical potential closer to zero when compared with commercial Ag/AgCl reference electrodes.
- FIG. 5 is a graph of the measured electrical potential of a reference electrode prepared as described hereinabove, when compared with a commercially available reference electrode, as a function of time, illustrating the stability of the present reference electrode.
- the total drift of the electrode between about 30 s and 1000 s is less than 0.03 mV.
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Abstract
Description
Claims (1)
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
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US11/070,329 US7658826B2 (en) | 2004-03-01 | 2005-03-01 | Reference electrode |
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
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US54898204P | 2004-03-01 | 2004-03-01 | |
US54898104P | 2004-03-01 | 2004-03-01 | |
US11/070,329 US7658826B2 (en) | 2004-03-01 | 2005-03-01 | Reference electrode |
Publications (2)
Publication Number | Publication Date |
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US20050191429A1 US20050191429A1 (en) | 2005-09-01 |
US7658826B2 true US7658826B2 (en) | 2010-02-09 |
Family
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Family Applications (1)
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US11/070,329 Expired - Fee Related US7658826B2 (en) | 2004-03-01 | 2005-03-01 | Reference electrode |
Country Status (4)
Country | Link |
---|---|
US (1) | US7658826B2 (en) |
EP (2) | EP1751531A1 (en) |
CA (2) | CA2558270A1 (en) |
WO (2) | WO2005085827A1 (en) |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP5183495B2 (en) | 2006-02-27 | 2013-04-17 | エドワーズ ライフサイエンシーズ コーポレイション | Method and apparatus using flex circuit technology for reference electrode channel fabrication |
US7438796B2 (en) * | 2006-08-28 | 2008-10-21 | Hach Company | Electrochemical chlorine sensor |
US20090038940A1 (en) * | 2007-08-07 | 2009-02-12 | Chung Yuan Christian University | Reference Electrode |
CN105445345B (en) * | 2015-11-12 | 2018-06-05 | 三诺生物传感股份有限公司 | A kind of preparation method of flexibility implant electrode |
JP6836244B2 (en) * | 2017-07-20 | 2021-02-24 | 島根県 | Flat plate type reference electrode and its manufacturing method |
WO2022245347A1 (en) * | 2021-05-19 | 2022-11-24 | Nova Biomedical Corporation | Solid-state reference electrode based on polymeric membrane |
Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4214968A (en) * | 1978-04-05 | 1980-07-29 | Eastman Kodak Company | Ion-selective electrode |
US4528085A (en) * | 1982-03-15 | 1985-07-09 | Fuji Photo Film Company, Ltd. | Ion selective electrode and process of preparing the same |
US4933048A (en) | 1988-02-16 | 1990-06-12 | I-Stat Corporation | Reference electrode, method of making and method of using same |
US4995960A (en) | 1987-11-24 | 1991-02-26 | Public Health Laboratory Service Board | Electrochemical electrodes |
US5360529A (en) * | 1991-08-24 | 1994-11-01 | Eastman Kodak Company | Reference half-cell electrode |
US5421983A (en) * | 1993-11-12 | 1995-06-06 | E. I. Du Pont De Nemours And Company | Anion selective electrodes containing fumed silica |
WO2000058720A1 (en) * | 1999-03-25 | 2000-10-05 | Infopia Co., Ltd. | A miniaturized solid-state reference electrode with self-diagnostic function |
US20010032785A1 (en) * | 2000-03-27 | 2001-10-25 | Cha Geun Sig | Planar reference electrode |
US20020134679A1 (en) * | 1999-02-01 | 2002-09-26 | Masaaki Terashima | Silver/silver halide electrode and ion-selective electrode element |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
EP0160997B1 (en) * | 1984-05-10 | 1991-08-07 | Fuji Photo Film Co., Ltd. | Ion selective electrode |
EP0661535A1 (en) * | 1993-12-15 | 1995-07-05 | Hitachi, Ltd. | Ion sensor |
JP2003533694A (en) * | 2000-05-18 | 2003-11-11 | メドトロニック,インコーポレイテッド | Ion-selective solid-state polymer membrane electrode |
-
2005
- 2005-03-01 WO PCT/US2005/006741 patent/WO2005085827A1/en active Application Filing
- 2005-03-01 EP EP05724312A patent/EP1751531A1/en not_active Withdrawn
- 2005-03-01 CA CA002558270A patent/CA2558270A1/en not_active Abandoned
- 2005-03-01 EP EP05724313A patent/EP1751528A1/en not_active Withdrawn
- 2005-03-01 WO PCT/US2005/006742 patent/WO2005085826A1/en active Application Filing
- 2005-03-01 CA CA002558275A patent/CA2558275A1/en not_active Abandoned
- 2005-03-01 US US11/070,329 patent/US7658826B2/en not_active Expired - Fee Related
Patent Citations (9)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4214968A (en) * | 1978-04-05 | 1980-07-29 | Eastman Kodak Company | Ion-selective electrode |
US4528085A (en) * | 1982-03-15 | 1985-07-09 | Fuji Photo Film Company, Ltd. | Ion selective electrode and process of preparing the same |
US4995960A (en) | 1987-11-24 | 1991-02-26 | Public Health Laboratory Service Board | Electrochemical electrodes |
US4933048A (en) | 1988-02-16 | 1990-06-12 | I-Stat Corporation | Reference electrode, method of making and method of using same |
US5360529A (en) * | 1991-08-24 | 1994-11-01 | Eastman Kodak Company | Reference half-cell electrode |
US5421983A (en) * | 1993-11-12 | 1995-06-06 | E. I. Du Pont De Nemours And Company | Anion selective electrodes containing fumed silica |
US20020134679A1 (en) * | 1999-02-01 | 2002-09-26 | Masaaki Terashima | Silver/silver halide electrode and ion-selective electrode element |
WO2000058720A1 (en) * | 1999-03-25 | 2000-10-05 | Infopia Co., Ltd. | A miniaturized solid-state reference electrode with self-diagnostic function |
US20010032785A1 (en) * | 2000-03-27 | 2001-10-25 | Cha Geun Sig | Planar reference electrode |
Non-Patent Citations (6)
Title |
---|
A. Mroz et al. "Disposable Reference Electrode" Analyst vol. 123, pp. 1373-1376 (1998). |
Bakker E, "Hydrophobic Membranes as Liquid Junction-Free Reference Elctrodes", Electroannalysis, VHC Publishers, Inc., US, vol. 11, No. 10-11, Jul. 1999, pp. 788-792. |
Eine, K. et al, "Towards a solid state reference elctrode", Sensors and Actuators B., Elsevier Sequoia S.A., Lausanne, CH, vol. 44, No. 1-3, Oct. 1997, pp. 381-388. |
Hyuk Jin Lee et al. "Solvent-Processible Polymer Membrane-Based Liquid Junction-Free Reference Electrode" Anal. Chem. 70, pp. 3377-3383 (1998). |
Johnson C. S. et al., "Reference Electrodes for Solid Polymer Electrolytes", Extended Abstracts, Electrochemical Society, Princeton, NJ, US, vol. 93/2, Oct. 10, 1993, pp. 66-67. |
Yoon H. J. et al., "Solid-state ion sensors with a liquid junction-free polymer membrance-based reference electrode for blood analysis" Sensors and Actuators B, Elsevier Sequoia S.A., Lausanne, CH, vol. 64, No. 1-3, Jun. 2000, pp. 8-14. |
Also Published As
Publication number | Publication date |
---|---|
CA2558275A1 (en) | 2005-09-15 |
US20050191429A1 (en) | 2005-09-01 |
CA2558270A1 (en) | 2005-09-15 |
WO2005085827A1 (en) | 2005-09-15 |
EP1751528A1 (en) | 2007-02-14 |
EP1751531A1 (en) | 2007-02-14 |
WO2005085826A1 (en) | 2005-09-15 |
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